CN112488317B - Simulation method and device in quantum control, classical computer and storage medium - Google Patents

Abstract

The present application discloses a simulation method in quantum control, and relates to the field of quantum control. The specific implementation scheme is as follows: obtaining the hardware parameters corresponding to the quantum system and the target quantum gate to be realized by the quantum system; obtaining the pulse function represented by discrete time slices; determining the discrete pulse function in the pulse function The target step size corresponding to the time slice, to obtain the pulse parameter value under the time length corresponding to the target step size according to the target step size corresponding to the time slice and the pulse function; based on the obtained target step size corresponding to the time length under the The pulse parameter value, and the hardware parameters of the quantum system, obtain the simulated quantum gate under the corresponding time length of the target step, until the target simulated quantum gate under the preset pulse duration is obtained, in this way, the distance between the target quantum gate and the target quantum gate is quickly obtained. The error satisfies the pre-set rules of the target simulation quantum gate.

Description

Simulation method, device, classical computer and storage medium in quantum control

technical field

The present application relates to the field of quantum computing, in particular to the field of quantum control.

Background technique

Quantum control is a bridge connecting quantum software and hardware, and an essential part of quantum computing. In quantum computing, in addition to the performance of quantum hardware (including the quality and quantity of qubits), it is also necessary to effectively control the quantum hardware, so that quantum algorithms and quantum information processing schemes can be efficiently executed. Specifically, quantum logic gates (ie, quantum gates) at the quantum software level need to be compiled into physical pulse signals that can be recognized by quantum hardware. In this process, the fidelity and speed of the compiled quantum gates are critical. Therefore, this means that it is necessary to quickly realize the quantum control technology of high-precision quantum gates, and how to realize quantum simulation quickly and accurately has become the core of quantum control technology.

SUMMARY OF THE INVENTION

The present application provides a simulation method, device, classical computer and storage medium in quantum control.

According to an aspect of the present application, a simulation method in quantum control is provided, comprising:

Obtain the hardware parameters corresponding to the quantum system and the target quantum gate that the quantum system needs to implement;

Obtain the pulse function represented by discrete time slices, wherein the start time of each time slice is the same as the pulse parameter value in the time period of the end time;

Determine the target step size corresponding to the discrete time slices in the pulse function, so as to obtain the pulse parameter value under the time length corresponding to the target step size according to the target step size corresponding to the time slice and the pulse function;

Based on the obtained pulse parameter values of the duration corresponding to the target step size and the hardware parameters of the quantum system, the simulated quantum gate of the duration corresponding to the target step size is obtained, until the target simulated quantum gate of the preset pulse duration is obtained gate, wherein the gap between the target simulation quantum gate and the target quantum gate under the preset pulse duration satisfies a preset rule.

According to another aspect of the present application, a simulation device in quantum control is provided, comprising:

a data acquisition unit for acquiring hardware parameters corresponding to the quantum system and target quantum gates that the quantum system needs to implement;

a function acquisition unit, configured to acquire a pulse function represented by discrete time slices, wherein the start time of each time slice is the same as the pulse parameter value in the time period of the end time;

a step size determination unit, configured to determine the target step size corresponding to the discrete time slices in the impulse function;

a pulse parameter value determination unit, configured to obtain the pulse parameter value under the time length corresponding to the target step length according to the target step size corresponding to the time slice and the pulse function;

The simulation unit is used for obtaining the simulated quantum gate under the time length corresponding to the target step size based on the obtained pulse parameter values corresponding to the target step size and the hardware parameters of the quantum system, until the preset pulse length is obtained The target simulation quantum gate under the preset pulse duration, wherein the gap between the target simulation quantum gate and the target quantum gate under the preset pulse duration satisfies a preset rule.

According to yet another aspect of the present application, a classical computer is provided, comprising:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein,

The memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method described above.

According to yet another aspect of the present application, there is provided a non-transitory computer-readable storage medium storing computer instructions for causing a computer to perform the above-described method.

According to yet another aspect of the present application, there is provided a computer program product comprising a computer program which, when executed by a processor, implements the method as described above.

According to the technology of the present application, quantum simulation can be realized quickly and accurately, and a target simulation quantum gate can be obtained, and the target simulation quantum gate is the target quantum gate planned to be realized, thus laying a foundation for a more efficient realization of the quantum gate.

It should be understood that the content described in this section is not intended to identify key or critical features of the embodiments of the application, nor is it intended to limit the scope of the application. Other features of the present application will become readily understood from the following description.

Description of drawings

The accompanying drawings are used for better understanding of the present solution, and do not constitute a limitation to the present application. in:

FIG. 1 is a schematic flowchart of the implementation of a simulation method in quantum control according to an embodiment of the present application;

2 is a schematic diagram 1 of discrete time slices in a specific scene according to an embodiment of the present application;

3 is a schematic diagram 2 of discrete time slices in a specific scene according to an embodiment of the present application;

FIG. 4 is a schematic flowchart in a specific example of a simulation method in quantum control according to an embodiment of the present application;

5 is a schematic structural diagram of a simulation device in quantum control according to an embodiment of the present application;

FIG. 6 is a block diagram of a classical computer of a simulation method in quantum control according to an embodiment of the present application.

Detailed ways

Exemplary embodiments of the present application are described below with reference to the accompanying drawings, which include various details of the embodiments of the present application to facilitate understanding, and should be considered as exemplary only. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the present application. Also, descriptions of well-known functions and constructions are omitted from the following description for clarity and conciseness.

An embodiment of the present invention provides a simulation method in quantum control. Specifically, FIG. 1 is a schematic diagram of an implementation flowchart of a simulation method in quantum control according to an embodiment of the present application. As shown in FIG. 1 , the process includes:

Step S101: Obtain hardware parameters corresponding to the quantum system and target quantum gates that the quantum system needs to implement.

Step S102: Acquire a pulse function represented by discrete time slices, wherein the start time of each time slice is the same as the pulse parameter value in the time period of the end time.

Step S103: Determine the target step size corresponding to the discrete time slice in the pulse function, so as to obtain the pulse parameter under the time length corresponding to the target step size according to the target step size corresponding to the time slice and the pulse function value.

Step S104: Based on the obtained pulse parameter values under the corresponding duration of the target step, and the hardware parameters of the quantum system, obtain a simulated quantum gate under the duration corresponding to the target step, until the preset pulse duration is obtained. A target simulation quantum gate, wherein the gap between the target simulation quantum gate and the target quantum gate under the preset pulse duration satisfies a preset rule.

In this way, since the solution of the present application can perform slicing processing on time, quantum simulation can be realized quickly and accurately, and the target simulation quantum gate obtained in the simulation process can be regarded as the target quantum gate that is planned to be realized. The foundation is laid for a more efficient implementation of gates.

In practical applications, the quantum system is a system formed by quantum hardware, and the hardware parameters are parameters corresponding to the quantum hardware. Harmonic strength and other parameters.

In an example, the following method can be used to discretize the time information of the impulse function, and then obtain the impulse function represented by discrete time slices. Specifically, the impulse function c _k (t) is approximately divided into time discrete The slice sequence of , where the starting time of the i (i≥1) slice is t _i-1 , the end time is t _i , and the time span (ie step size) is Δt _i =t _i -t _i-1 , the height of the ith (i≥1) slice (that is, the pulse parameter value) is constant as

In a specific example of the solution of the present application, the target step size corresponding to each of the time slices is the same or different. For example, after discretizing the time information of the impulse function, the time span (that is, the target step size) of each time slice is the same, as shown in the discretization processing result shown in Figure 2. Here, each time slice The corresponding step size is the same, and the height of the pulse (pulse parameter value) in each time slice is constant. Of course, as shown in Figure 3, the time spans (that is, the target step size) of different time slices are different, or need not be the same. The same, but the height of the pulse (pulse parameter value) within each time slice is constant. In this way, the purpose of dynamically determining the target step size is achieved, which lays a foundation for simplifying the calculation process and improving the calculation efficiency, and also lays a foundation for the subsequent rapid and accurate simulation of the target quantum gate. Moreover, since the target step size can be the same or different, the error (the gap between the target simulation quantum gate and the target quantum gate) and the computational efficiency can be taken into account, thus improving the flexibility of the solution of the present application.

In a specific example of the solution of the present application, the target step size can be obtained in the following manner. Specifically, the above-mentioned determining the target step size corresponding to the discrete time slices in the pulse function includes: obtaining a first initialization step length (for example, a preset value); based on the first initialization step size and the pulse function, the difference between the pulse parameter values at adjacent moments is obtained; after determining the pulse parameter values at the adjacent moments When the difference value is less than the preset pulse threshold, and the period corresponding to the first initialization step does not exceed the preset pulse duration (that is, the time period for which the target step is currently determined does not exceed the preset pulse duration) time), the first initialization step size is used as the target step size. For example, as shown in FIG. 3 , it is assumed that the current period of the target step size to be determined is the (t ₁ , t ₂ ) period, and the preset pulse time is t _g , at this time, only the (t ₁ , t ₂ ) period is required Within t _g , for example, t _g corresponds to time t ₃ in Figure 3. At this time, t ₂ is before t ₃ , that is, the (t ₁ , t ₂ ) period is within t _g . At this time, all the The first initialization step size is used as the target step size. Otherwise, stop the operation.

In this way, the target step size corresponding to each time slice is obtained, which lays a foundation for simplifying the calculation process, and also lays a foundation for the subsequent rapid and accurate simulation of the target quantum gate.

In a specific example of the solution of the present application, the target step size can be obtained in the following manner. Specifically, the above-mentioned determining the target step size corresponding to the discrete time slices in the pulse function includes: obtaining a second initialization step The difference between the pulse parameter values at adjacent moments is calculated based on the second initialization step size and the pulse function; when it is determined that the difference between the pulse parameter values at the adjacent moments is greater than or equal to a preset value In the case of the pulse threshold, the second initialization step is adjusted until the difference between the adjusted pulse parameter values at adjacent moments is less than the pulse threshold; after determining the adjusted second initialization step Under the condition that the corresponding period does not exceed the preset pulse duration, the adjusted second initialization step size in which the difference between the pulse parameter values at adjacent moments is less than the pulse threshold value is used as the target step size.

Similar to the above example, this example shows the situation that the difference between the pulse parameter values at the adjacent moments is greater than or equal to the preset pulse threshold. In this case, the target step size can be adjusted, for example, the target step size can be reduced , so as to satisfy the condition that the difference between the pulse parameter values at adjacent moments is less than the pulse threshold. In this way, a scheme of dynamically determining the step size is improved, which lays a foundation for simplifying the calculation process, and also lays a foundation for the subsequent fast and accurate simulation to obtain the target quantum gate.

Here, it is worth noting that, in practical applications, the first initialization step size and the second initialization step size may be unified as a preset preset step size set by default.

In a specific example of the solution of the present application, the data processing rule of the time evolution operator can also be obtained in the following manner, and then a simulated quantum gate can be obtained based on the data processing rule; specifically, before step S104, the method further includes: determining the The total Hamiltonian corresponding to the quantum system is obtained, and the first mapping relationship between the time evolution operator and the total Hamiltonian is obtained. For example, the first mapping relationship can be specifically the linear Schrödinger equation; wherein, the total The Hamiltonian includes at least an impulse Hamiltonian, and the impulse Hamiltonian includes the impulse function related to time information used to control the impulse; further, based on the impulse function represented by discrete time slices, Mathematically transform the first mapping relationship to determine the data processing rule of the time evolution operator; finally, after the data processing rule is determined, the pulse parameter value based on the obtained target step corresponding to the duration , and the hardware parameters of the quantum system, to obtain the simulated quantum gate under the time length corresponding to the target step size, which specifically includes: the obtained pulse parameter value under the time length corresponding to the target step size and the hardware of the quantum system The parameters are input into the data processing rules, and the simulated quantum gate under the time length corresponding to the target step size is obtained. That is to say, in practical applications, after discretizing the time information of the impulse function, the total Hamiltonian can be mathematically changed based on the impulse function represented by the discrete time slice, and then a data processing rule can be obtained, Using the data processing rule, the simulated quantum gate can be obtained based on the pulse parameter value and the hardware parameters of the quantum system. In this way, quantum simulation is realized, and a target simulation quantum gate is obtained, and the target simulation quantum gate is the target quantum gate planned to be realized, thus laying a foundation for a more efficient realization of the quantum gate.

In this way, since the solution of the present application can perform slicing processing on time, quantum simulation can be realized quickly and accurately, and the target simulation quantum gate obtained in the simulation process can be regarded as the target quantum gate that is planned to be realized. The foundation is laid for a more efficient implementation of gates.

The solution of the present application will be described in further detail below with reference to specific examples. Specifically, this example proposes a quantum simulation method for quantum control and solving based on ordinary differential equations, which can also be called discrete-time approximate solution based on dynamic step size. method of quantum simulation. The solution of the present application can dynamically adjust the step size of discrete time in the evolution process of the computing system according to the actual required target quantum gate in the process of generating the pulse function used to control the quantum gate, and then adjust the pulse parameters used to obtain the target quantum gate Therefore, the time required to obtain the target pulse parameter value of the target quantum gate is greatly reduced, and the accuracy of the operation result can be guaranteed.

In practical applications, the experimenter can directly apply the scheme of the present application to the experiment according to the different usage scenarios, or further improve the fidelity of the quantum gate based on the pulse function given by the technical scheme and combine with other optimization schemes. This is not limited.

The following is a detailed description of the solution of the present application from two aspects; the first part illustrates the core idea and key steps of the solution of the present application; the second part focuses on showing the effects and advantages of the solution of the present application. specifically,

In the first part, the steps of obtaining the time evolution operator after optimizing the "Runge-Kutta" algorithm based on the "discrete-time approximate solution method of dynamic step size", that is, the discrete-time approximate solution method combining dynamic step size and Runge-Kutta The algorithm obtains the time evolution operator and the specific simulation process.

The solution of the present application provides a new generation solution for control pulses (that is, pulse functions) for controlling quantum gates. ”) to process the impulse function to obtain the time evolution operator, which is the simulated quantum gate calculated in the simulation process. In the above solution process, the time information of the impulse function is sliced, And the target step size corresponding to each time slice can be dynamically determined. In this way, it is possible to quickly simulate the target simulation quantum gate. The target simulation quantum gate is the target quantum gate that is planned to be realized. In this way, it is more efficient for the quantum gate. The realization laid the foundation. In this process, it is only necessary to determine the target quantum gate to be realized and the relevant parameters of the quantum hardware, and then the optimized target pulse value to be applied can be output quickly, stably and accurately.

More specifically, the solution of the present application adopts the first-order "dynamic step method" and "Runge-Kutta" hybrid method in the initialization process of the impulse function to solve the time-dependent (that is, the time-containing time) satisfied by the time evolution operator. parameters, hereinafter referred to as time-dependent) Schrodinger equation, and further use the Nelder-Mead optimization method to obtain the pulse parameters.

Here, it should be noted that other optimization algorithms may also be selected for the optimization method provided in this example, that is, the Nelder-Mead optimization method is only used as an example, and is not used to limit the solution of the present application.

Further, in order to illustrate the solution of the present application more clearly, the following takes the realization of a superconducting single-bit quantum gate as an example to fully illustrate the core idea and key steps of the solution of the present application. It is necessary to point out that the solution of the present application also supports multi-qubit quantum gates and other quantum systems, which is not limited.

The core idea of the solution of the present application includes: using the "dynamic step method" method to solve the Schrödinger equation satisfied by a quantum system (that is, a system formed by quantum hardware), specifically:

Given the Hamiltonian H(t) of a quantum system, the dynamic equation satisfied by the time evolution operator U(t) can be described by a linear Schrödinger equation (ie, equation (1) below):

为普朗克常数。欲求解该含时微分方程，采用了“动态步长的离散时间近似求解方法”。以下详细介绍“动态步长的离散时间近似求解方法”，包括：where i is the imaginary unit,

is Planck's constant. To solve this time-dependent differential equation, a "discrete-time approximate solution method with dynamic steps" is used. The following details the "Discrete-Time Approximate Solution Method for Dynamic Steps", including:

In the quantum optimal control problem, the Hamiltonian of a quantum system can be expressed as:

H _total (t)=H _drift +H _ctrl (t),(2)

Among them, H _total (t) corresponds to H (t) in the above formula (1), and H _drift is the drift Hamiltonian when it is not included, which generally describes the hardware structure of the quantum system. H _ctrl (t) is the Hamiltonian including the impulse function, which can be written as:

如果每一个切片序列的时间跨度一样，则得到如图2所示的离散化处理结果，这里，由于在每一个切片内，脉冲的高度(脉冲参数值)是恒定不变的，即对应了一个不含时的哈密顿

因而可以使用矩阵指数的解法来求解其时间演化算符：Among them, c _k (t) (k=1,2,...,N) is the envelope function describing the kth pulse waveform, which is generally time-dependent; H _k is the control algorithm that does not include time. symbol (characterizing the way the pulse is coupled to the quantum system). It can be seen that in the quantum optimal control problem, the time-dependent part only describes the pulse waveform (ie, the pulse function). Based on this characteristic, the impulse function c _k (t) in the evolution process is approximately divided into a time-discrete slice sequence, where the start time of the i (i≥1) slice is t _i-1 and the end time is t _i , the time span is Δt _i =t _i -t _i-1 , the height of the i-th (i≥1) slice is constant as

If the time span of each slice sequence is the same, the discretization processing result shown in Figure 2 will be obtained. Here, since in each slice, the height of the pulse (pulse parameter value) is constant, that is, it corresponds to a timeless hamilton

Therefore, we can use the solution of matrix exponential to solve its time evolution operator:

U(t)=exp(-iH _i Δt _i ),(4)

where exp represents the matrix exponential operation, and H _i represents H _total at time t _i . Here, since H _i is related to the impulse function, the time evolution operator U(t) is also related to the impulse function. In this way, after initializing the pulse parameter value of the pulse function, the U value corresponding to the initialized pulse parameter value can be obtained based on formula (4). The U value is the quantum gate in the simulation process, that is, the simulation quantum gate.

Here, it can be seen from Figure 2 that the larger the time span of the slice, the larger the error, and the shorter the time consumed by the calculation. The smaller the time span of the slice, the smaller the error, but the longer the calculation time. Based on this, the present application can dynamically select an appropriate step size based on the specific properties of the impulse function, so as to maximize the calculation speed within the tolerance range.

Of course, in order to simplify the calculation process, improve the calculation efficiency, and ensure that the calculation results meet the accuracy requirements, the time spans (that is, the target step size) of different time slices are different, or do not need to be the same. As shown in Figure 3, each time slice The steps corresponding to each time slice are different, but the height of the pulse (pulse parameter value) in each time slice is constant.

As shown in Figure 4, the specific steps of the scheme of the present application include:

Step 1: Input, that is, input the preset pulse time t _g , the drift Hamiltonian H _drift excluding the time, the Hamiltonian H _ctrl including the pulse function, and the corresponding pulse function _ck (t), the default step size δt , slice maximum change threshold (pulse threshold) μ.

Step 2: Initialize the total time evolution operator (that is, the evolution operator described in Figure 4) U(t)=I, that is, when t ₀ =0, U(0)=I, where I is the identity matrix, t ₀ =0.

Step 3: Dynamically adjust the discrete time step according to the degree of change, including:

(1) Calculate the initial step size: Δt=min{δt,t _g -t _j }.

(2) Calculate the function value of the impulse function: set the starting time point as t _j , and calculate c(t _j )=∑ _k c _k (t _j ). And according to the step size Δt, the next moment c(t _j +Δt)=∑ _k c _k (t _j +Δt) is calculated.

(3) Calculate the degree of change: Δc(t _j )=c(t _j +Δt)-c(t _j ). If Δc(t _j ) is greater than the preset threshold μ, then Δt is set to Δt/2, and the first step (1) in step 3 is performed again. If Δc(t _j ) is smaller than the preset threshold μ, go to step 4 .

,其中，式中所述的H为H_total，即t_j+Δt时刻的H_total，i是虚数，换言之，得到t_j+Δt时刻仿真量子门U_j(t)。更新U(t)←U_j(t)U(t)以及t_j←t_j+Δt。Step 4: Calculate the time evolution operator: According to the step size Δt determined in step 3, use the matrix index to calculate the time evolution operator:

, where H described in the formula is H _total , that is, H _total at time t _j +Δt, and i is an imaginary number, in other words, the simulated quantum gate U _j (t) at time t _j +Δt is obtained. Update U(t)←Uj(t)U(t) and _tj ← _{tj +} Δt.

Step 5: Repeat steps 3 and 4 until t _j ≥ t _g (that is, the current time reaches the preset maximum time, and the preset maximum time is the preset pulse time).

Step 6: The returned U(t _g ) is the time evolution operator of the entire impulse function, that is, the target simulation quantum gate, and the target simulation quantum gate can be regarded as the expected target quantum gate, in other words, the target simulation quantum gate The target quantum gate can be realized by applying the target pulse parameter value at time t _g corresponding to the quantum gate to the quantum system. Moreover, the time evolution operator fully considers the functional properties of the impulse function and meets the requirements of quantum gate error.

The second part presents the effects of this technical solution, including:

In order to verify the effectiveness and advantages of the technical solutions described above, the controlled Z gate (Controlled-Z gate) of the superconducting qubit was tested as an example. In the following tests, the optimization algorithm will be used in conjunction with the "discrete-time approximate solution method of dynamic step size" to calculate the pulse parameters of the controlled Z-gate under given hardware parameters, so as to achieve a high-precision controlled Z-gate; The Runge-Kutta algorithm benchmarks the operation results. To simplify the model, only three-level quantum systems are considered here (that is, each superconducting qubit is regarded as a three-level quantum system), and two directly coupled superconducting qubits are used here, and their superconducting qubit frequency are ω ₁ =5.805×2πGHZ and ω ₂ =5.205×2πGHZ, respectively, the detuning strengths of superconducting qubits are: α ₁ =-0.217×2πGHZ and α ₂ =-0.226×2πGHZ; the target quantum gate U _goal takes is the controlled Z gate, namely:

In general, by applying a magnetic flux to the superconducting qubit 1 (ie, tuning the frequency of the superconducting qubit 1), a controlled Z-gate can be realized. Based on this, the Hamiltonian of the above scheme can be expressed as:

where c(t) is the impulse function, which is expressed as a square wave represented by the error function, namely:

Among them, A, s, t _s , _te are the pulse parameters in the pulse function that need to be optimized to obtain the high-fidelity Controlled-Z gate.

The solution of the present application is used for optimization, and the "discrete-time approximate solution method of dynamic step size" is used to calculate the time evolution operator U _real of the Hamiltonian of the above formula (6), that is, the target simulation quantum gate, and project it. Go to the superconducting qubit space, and then calculate the distortion function of the simulated quantum gate by the following formula:

where Tr represents the trace of the matrix. This distortion function is the optimization objective function used in this test, and the objective of optimization is to minimize this objective function.

The test results are shown below. First, compare the solution time obtained by the method described in the solution of the present application and the existing method. Here, the maximum change threshold μ=0.2 in the solution of the present application, at this time, the results obtained by the solution of the present application and the existing method are as follows:

The maximum change threshold μ=0.002 in the solution of the present application, at this time, the results obtained by the solution of the present application and the existing method are as follows:

The time-consuming and fidelity of the existing algorithm using the same precision, such as the existing Runge-Kutta method, is as follows:

Therefore, the use of the dynamic slicing scheme of the present application can greatly improve the calculation speed, and the error is within a controllable range.

Compared with other existing quantum simulation methods used in quantum regulation, the proposed solution has significant advantages in the following points:

First, the speed is fast, that is, compared with the traditional Runge-Kutta technology, the pulse generation speed of the solution of the present application can be increased by ten times or dozens of times.

Second, strong practicability, that is, in superconducting quantum computing, in the case of using square wave-like pulses, the solution of the present application can significantly increase the speed and has strong practicability.

Third, the scalability is strong, that is, more pulses can be added as needed to obtain more abundant pulse waveforms. In addition, the control channel can also be expanded.

Fourth, the flexibility is high, that is, different maximum change thresholds can be set according to actual needs to control the calculation accuracy, so it is more flexible than the existing solution.

The solution of the present application also provides a simulation device in quantum control, as shown in FIG. 5 , including:

A data acquisition unit 501, configured to acquire hardware parameters corresponding to the quantum system and target quantum gates to be implemented by the quantum system;

A function obtaining unit 502, configured to obtain a pulse function represented by discrete time slices, wherein the start time of each time slice is the same as the pulse parameter value in the time period of the end time;

Step size determination unit 503, configured to determine the target step size corresponding to the discrete time slices in the impulse function;

a pulse parameter value determination unit 504, configured to obtain the pulse parameter value under the time length corresponding to the target step length according to the target step length corresponding to the time slice and the pulse function;

The simulation unit 505 is configured to obtain the simulated quantum gate under the time length corresponding to the target step size based on the obtained pulse parameter value corresponding to the target step size and the hardware parameters of the quantum system, until a preset pulse is obtained The target simulation quantum gate under the duration, wherein the gap between the target simulation quantum gate and the target quantum gate under the preset pulse duration satisfies a preset rule.

In a specific example of the solution of the present application, the target step size corresponding to each of the time slices is the same or different.

In a specific example of the solution of the present application, the step size determining unit includes:

The first step is to obtain the subunit, which is used to obtain the first initialization step;

a first difference calculation subunit, configured to calculate the difference between pulse parameter values at adjacent moments based on the first initialization step size and the pulse function;

The first step length determination subunit is used to determine that the difference between the pulse parameter values at the adjacent moments is less than a preset pulse threshold, and the time period corresponding to the first initialization step size does not exceed the preset value In the case of the pulse duration, the first initialization step size is used as the target step size.

In a specific example of the solution of the present application, the step size determining unit includes:

The second step size obtaining subunit is used to obtain the second initialization step size;

a second difference calculation subunit, configured to calculate the difference between pulse parameter values at adjacent moments based on the second initialization step size and the pulse function;

The step size adjustment subunit is configured to adjust the second initialization step size when it is determined that the difference between the pulse parameter values at the adjacent moments is greater than or equal to a preset pulse threshold value, until the adjusted The difference between the pulse parameter values at adjacent moments is less than the pulse threshold;

The second step size determination subunit is configured to make the difference between the pulse parameter values at adjacent moments less than The adjusted second initialization step size of the pulse threshold is used as the target step size.

In a specific example of the solution of the present application, it further includes: a data processing rule determination unit; wherein,

The data processing rule determination unit is configured to determine the total Hamiltonian corresponding to the quantum system, and obtain the first mapping relationship between the time evolution operator and the total Hamiltonian; wherein, the total Hamiltonian The stop includes at least an impulse Hamiltonian, and the impulse Hamiltonian includes the impulse function related to the time information used to control the impulse; based on the impulse function represented by discrete time slices, for the first A mapping relationship is mathematically transformed to determine the data processing rule of the time evolution operator;

The simulation unit is further configured to input the obtained pulse parameter value and the hardware parameter of the quantum system under the corresponding duration of the target step into the data processing rule to obtain the simulation under the duration corresponding to the target step. Quantum gate.

In this way, since the solution of the present application can perform slicing processing on time, quantum simulation can be realized quickly and accurately, and the target simulation quantum gate obtained in the simulation process can be regarded as the target quantum gate that is planned to be realized. The groundwork is laid for a more efficient implementation of gates.

According to the embodiments of the present application, the present application further provides a classical computer, a readable storage medium, and a computer program product.

As shown in FIG. 6 , it is a block diagram of a classical computer of a simulation method in quantum control according to an embodiment of the present application. Classical computer is intended to refer to various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The components shown herein, their connections and relationships, and their functions are by way of example only, and are not intended to limit implementations of the application described and/or claimed herein.

As shown in FIG. 6, the classic computer includes: one or more processors 601, a memory 602, and interfaces for connecting various components, including a high-speed interface and a low-speed interface. The various components are interconnected using different buses and may be mounted on a common motherboard or otherwise as desired. The processor may process instructions executed within a classical computer, including instructions stored in or on memory to display graphical information of the GUI on an external input/output device, such as a display device coupled to the interface. In other embodiments, multiple processors and/or multiple buses may be used with multiple memories and multiple memories, if desired. Likewise, multiple classic computers can be connected, with each device providing some of the necessary operations (eg, as an array of servers, a group of blade servers, or a multiprocessor system). A processor 601 is taken as an example in FIG. 6 .

The memory 602 is the non-transitory computer-readable storage medium provided by the present application. Wherein, the memory stores instructions executable by at least one processor, so that the at least one processor executes the simulation method in quantum control provided by the present application. The non-transitory computer-readable storage medium of the present application stores computer instructions for causing the computer to execute the simulation method in quantum control provided by the present application.

As a non-transitory computer-readable storage medium, the memory 602 can be used to store non-transitory software programs, non-transitory computer-executable programs and modules, such as program instructions/modules ( For example, the data acquisition unit 501, the function acquisition unit 502, the step size determination unit 503, the pulse parameter value determination unit 504, the simulation unit 505 shown in FIG. 5, and the data processing rule determination unit not shown in FIG. 5). The processor 601 executes various functional applications and data processing of the server by running the non-transitory software programs, instructions and modules stored in the memory 602, that is, implementing the simulation method in quantum control in the above method embodiments.

The memory 602 can include a stored program area and a stored data area, wherein the stored program area can store an operating system, an application program required for at least one function; the stored data area can store a computer created according to the use of a classical computer for simulation methods in quantum control data etc. Additionally, memory 602 may include high-speed random access memory, and may also include non-transitory memory, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid state storage device. In some embodiments, the memory 602 may optionally include memory located remotely from the processor 601, and these remote memories may be connected via a network to a classical computer of the simulation method in quantum control. Examples of such networks include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

The classical computer of the simulation method in quantum control may further include: an input device 603 and an output device 604 . The processor 601 , the memory 602 , the input device 603 and the output device 604 may be connected by a bus or in other ways, and the connection by a bus is taken as an example in FIG. 6 .

The input device 603 can receive input numerical or character information, as well as generate key signal input related to user settings and functional control of classical computers for simulation methods in quantum control, such as touch screens, keypads, mice, trackpads, touchpads, An input device such as a pointing stick, one or more mouse buttons, trackball, joystick, etc. Output devices 604 may include display devices, auxiliary lighting devices (eg, LEDs), haptic feedback devices (eg, vibration motors), and the like. The display device may include, but is not limited to, a liquid crystal display (LCD), a light emitting diode (LED) display, and a plasma display. In some implementations, the display device may be a touch screen.

Various implementations of the systems and techniques described herein can be implemented in digital electronic circuitry, integrated circuit systems, application specific ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include being implemented in one or more computer programs executable and/or interpretable on a programmable system including at least one programmable processor that The processor, which may be a special purpose or general-purpose programmable processor, may receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device an output device.

These computational programs (also referred to as programs, software, software applications, or codes) include machine instructions for programmable processors, and may be implemented using high-level procedural and/or object-oriented programming languages, and/or assembly/machine languages calculation program. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, apparatus, and/or apparatus for providing machine instructions and/or data to a programmable processor ( For example, magnetic disks, optical disks, memories, programmable logic devices (PLDs), including machine-readable media that receive machine instructions as machine-readable signals. The term "machine-readable signal" refers to any signal used to provide machine instructions and/or data to a programmable processor.

To provide interaction with a user, the systems and techniques described herein may be implemented on a computer having a display device (eg, a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user ); and a keyboard and pointing device (eg, a mouse or trackball) through which a user can provide input to the computer. Other kinds of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (eg, visual feedback, auditory feedback, or tactile feedback); and can be in any form (including acoustic input, voice input, or tactile input) to receive input from the user.

The systems and techniques described herein may be implemented on a computing system that includes back-end components (eg, as a data server), or a computing system that includes middleware components (eg, an application server), or a computing system that includes front-end components (eg, a user's computer having a graphical user interface or web browser through which a user may interact with implementations of the systems and techniques described herein), or including such backend components, middleware components, Or any combination of front-end components in a computing system. The components of the system may be interconnected by any form or medium of digital data communication (eg, a communication network). Examples of communication networks include: Local Area Networks (LANs), Wide Area Networks (WANs), and the Internet.

A computer system can include clients and servers. Clients and servers are generally remote from each other and usually interact through a communication network. The relationship of client and server arises by computer programs running on the respective computers and having a client-server relationship to each other. The server can be a cloud server, also known as a cloud computing server or a cloud host. It is a host product in the cloud computing service system to solve the traditional physical host and virtual private server (VPS) services. Weak scalability defect. The server can also be a server of a distributed system, or a server combined with a blockchain.

According to the technical solutions of the embodiments of the present application, since the time can be sliced, quantum simulation can be realized quickly and accurately, and the target simulation quantum gate obtained in the simulation process can be regarded as the target quantum gate that is planned to be realized, This lays the foundation for a more efficient implementation of quantum gates.

It should be understood that steps may be reordered, added or deleted using the various forms of flow shown above. For example, the steps described in the present application can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in the present application can be achieved, no limitation is imposed herein.

The above-mentioned specific embodiments do not constitute a limitation on the protection scope of the present application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims (12)

1. A simulation method in quantum control, comprising:

acquiring hardware parameters corresponding to a quantum system and a target quantum gate required to be realized by the quantum system;

obtaining a pulse function represented based on discrete time slices, wherein the pulse parameter values in the time periods of the starting time and the ending time of each time slice are the same;

determining a target step length corresponding to the time slice which is dispersed in the pulse function, and obtaining a pulse parameter value under the duration corresponding to the target step length according to the target step length corresponding to the time slice and the pulse function;

and obtaining a simulation quantum gate under the duration corresponding to the target step length based on the obtained pulse parameter value under the duration corresponding to the target step length and the hardware parameter of the quantum system until obtaining a target simulation quantum gate under a preset pulse duration, wherein the difference between the target simulation quantum gate and the target quantum gate under the preset pulse duration meets a preset rule.

2. The method of claim 1, wherein the target step size for each time slice is the same or different.

3. The method of claim 1 or 2, wherein said determining a target step size corresponding to said time slice discrete in said pulse function comprises:

acquiring a first initialization step length;

calculating to obtain a difference value between pulse parameter values at adjacent moments based on the first initialization step length and the pulse function;

and taking the first initialization step length as the target step length under the conditions that the difference value between the pulse parameter values at the adjacent moments is smaller than a preset pulse threshold value and the time period corresponding to the first initialization step length does not exceed the preset pulse duration.

4. The method of claim 1 or 2, wherein said determining a target step size corresponding to said time slice discrete in said pulse function comprises:

acquiring a second initialization step length;

calculating to obtain a difference value between pulse parameter values at adjacent moments based on the second initialization step length and the pulse function;

under the condition that the difference value between the pulse parameter values at the adjacent moments is determined to be larger than or equal to a preset pulse threshold value, adjusting the second initialization step length until the difference value between the adjusted pulse parameter values at the adjacent moments is smaller than the pulse threshold value;

and under the condition that the time period corresponding to the adjusted second initialization step length does not exceed the preset pulse duration, taking the adjusted second initialization step length of which the difference value between the pulse parameter values at the adjacent moments is smaller than the pulse threshold value as the target step length.

5. The method of claim 1, further comprising:

determining a total Hamiltonian corresponding to the quantum system, and obtaining a first mapping relation between a time evolution operator and the total Hamiltonian; wherein the total Hamiltonian at least comprises a pulse Hamiltonian, and the pulse Hamiltonian comprises the pulse function related to time information for controlling the pulse;

performing mathematical transformation on the first mapping relation based on the pulse function represented by the discrete time slice to determine a data processing rule of the time evolution operator;

wherein, the obtaining of the simulated quantum gate at the duration corresponding to the target step length based on the obtained pulse parameter value at the duration corresponding to the target step length and the hardware parameter of the quantum system includes:

and inputting the obtained pulse parameter value under the duration corresponding to the target step length and the hardware parameter of the quantum system into the data processing rule to obtain the simulation quantum gate under the duration corresponding to the target step length.

6. A simulation apparatus in quantum control, comprising:

the data acquisition unit is used for acquiring hardware parameters corresponding to the quantum system and a target quantum gate required to be realized by the quantum system;

the function acquisition unit is used for acquiring a pulse function represented based on discrete time slices, wherein the pulse parameter value in the time period of the starting time and the ending time of each time slice is the same;

a step length determining unit, configured to determine a target step length corresponding to the time slice dispersed in the pulse function;

a pulse parameter value determining unit, configured to obtain a pulse parameter value for a duration corresponding to the target step length according to the target step length corresponding to the time slice and the pulse function;

and the simulation unit is used for obtaining a simulation quantum gate under the time length corresponding to the target step length based on the obtained pulse parameter value under the time length corresponding to the target step length and the hardware parameter of the quantum system until obtaining a target simulation quantum gate under a preset pulse time length, wherein the difference between the target simulation quantum gate and the target quantum gate under the preset pulse time length meets a preset rule.

7. The apparatus of claim 6, wherein the target step size for each time slice is the same or different.

8. The apparatus of claim 6 or 7, wherein the step size determining unit comprises:

a first step length obtaining subunit, configured to obtain a first initialization step length;

the first difference calculating subunit is used for calculating and obtaining the difference between the pulse parameter values at adjacent moments based on the first initialization step length and the pulse function;

and the first step length determining subunit is configured to, when it is determined that the difference between the pulse parameter values at the adjacent times is smaller than a preset pulse threshold and a time period corresponding to the first initialization step length does not exceed the preset pulse time length, take the first initialization step length as the target step length.

9. The apparatus of claim 6 or 7, wherein the step size determining unit comprises:

a second step length obtaining subunit, configured to obtain a second initialization step length;

the second difference calculating subunit is configured to calculate a difference between pulse parameter values at adjacent times based on the second initialization step and the pulse function;

a step length adjusting subunit, configured to, when it is determined that the difference between the pulse parameter values at the adjacent times is greater than or equal to a preset pulse threshold, adjust the second initialization step length until the adjusted difference between the pulse parameter values at the adjacent times is smaller than the pulse threshold;

and the second step length determining subunit is configured to, when it is determined that the time period corresponding to the adjusted second initialization step length does not exceed the preset pulse duration, take the adjusted second initialization step length, in which the difference between pulse parameter values at adjacent times is smaller than the pulse threshold, as the target step length.

10. The apparatus of claim 6, further comprising: a data processing rule determining unit; wherein,

the data processing rule determining unit is used for determining a total Hamiltonian corresponding to the quantum system and obtaining a first mapping relation between a time evolution operator and the total Hamiltonian; wherein the total Hamiltonian at least comprises a pulse Hamiltonian, and the pulse Hamiltonian comprises the pulse function related to time information for controlling the pulse; performing mathematical transformation on the first mapping relation based on the pulse function represented by the discrete time slice to determine a data processing rule of the time evolution operator;

and the simulation unit is further configured to input the obtained pulse parameter value of the target step length in the time length corresponding to the target step length and the obtained hardware parameter of the quantum system into the data processing rule, so as to obtain the simulated quantum gate of the target step length in the time length corresponding to the target step length.

11. A classic computer, comprising:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein,

the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of claims 1-5.

12. A non-transitory computer readable storage medium having stored thereon computer instructions for causing a computer to perform the method of any one of claims 1-5.

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